DESCRIPTION

rdiff-backup is a script, written in python(1) that backs up one direc-
tory to another. The target directory ends up a copy (mirror) of the
source directory, but extra reverse diffs are stored in a special sub-
directory of that target directory, so you can still recover files lost
some time ago. The idea is to combine the best features of a mirror
and an incremental backup. rdiff-backup also preserves symlinks, spe-
cial files, hardlinks, permissions, uid/gid ownership, and modification
times.
rdiff-backup can also operate in a bandwidth efficient manner over a
pipe, like rsync(1). Thus you can use ssh and rdiff-backup to securely
back a hard drive up to a remote location, and only the differences
will be transmitted. Using the default settings, rdiff-backup requires
that the remote system accept ssh connections, and that rdiff-backup is
installed in the user's PATH on the remote system. For information on
other options, see the section on REMOTEOPERATION.
Note that you shouldnotwritetothemirrordirectory except with
rdiff-backup. Many of the increments are stored as reverse diffs, so
if you delete or modify a file, you may lose the ability to restore
previous versions of that file.
Finally, this man page is intended more as a precise description of the
behavior and syntax of rdiff-backup. New users may want to check out
the examples.html file included in the rdiff-backup distribution.

OPTIONS

-b,--backup-mode
Force backup mode even if first argument appears to be an incre-
ment or mirror file.
--calculate-average
Enter calculate average mode. The arguments should be a number
of statistics files. rdiff-backup will print the average of the
listed statistics files and exit.
--carbonfile
Enable backup of MacOS X carbonfile information.
--check-destination-dir
If an rdiff-backup session fails, running rdiff-backup with this
option on the destination dir will undo the failed directory.
This happens automatically if you attempt to back up to a direc-
tory and the last backup failed.
--compare
This is equivalent to '--compare-at-timenow'--compare-at-timetime
Compare a directory with the backup set at the given time. This
can be useful to see how archived data differs from current
data, or to check that a backup is current. This only compares
metadata, in the same way rdiff-backup decides whether a file
has changed.
--compare-full
This is equivalent to '--compare-full-at-timenow'--compare-full-at-timetime
Compare a directory with the backup set at the given time. To
compare regular files, the repository data will be copied in its
entirety to the source side and compared byte by byte. This is
the slowest but most complete compare option.
--compare-hash
This is equivalent to '--compare-hash-at-timenow'--compare-hash-at-timetime
Compare a directory with the backup set at the given time. Reg-
ular files will be compared by computing their SHA1 digest on
the source side and comparing it to the digest recorded in the
metadata.
--create-full-path
Normally only the final directory of the destination path will
be created if it does not exist. With this option, all missing
directories on the destination path will be created. Use this
option with care: if there is a typo in the remote path, the
remote filesystem could fill up very quickly (by creating a
duplicate backup tree). For this reason this option is primarily
aimed at scripts which automate backups.
--current-timeseconds
This option is useful mainly for testing. If set, rdiff-backup
will use it for the current time instead of consulting the
clock. The argument is the number of seconds since the epoch.
--excludeshell_pattern
Exclude the file or files matched by shell_pattern. If a direc-
tory is matched, then files under that directory will also be
matched. See the FILESELECTION section for more information.
--exclude-device-files
Exclude all device files. This can be useful for security/per-
missions reasons or if rdiff-backup is not handling device files
correctly.
--exclude-fifos
Exclude all fifo files.
--exclude-filelistfilename
Excludes the files listed in filename. If filename is handwrit-
ten you probably want --exclude-globbing-filelist instead. See
the FILESELECTION section for more information.
--exclude-filelist-stdin
Like --exclude-filelist, but the list of files will be read from
standard input. See the FILESELECTION section for more infor-
mation.
--exclude-globbing-filelist filename
Like --exclude-filelist but each line of the filelist will be
interpreted according to the same rules as --include and
--exclude.--exclude-globbing-filelist-stdin
Like --exclude-globbing-filelist, but the list of files will be
read from standard input.
--exclude-other-filesystems
Exclude files on file systems (identified by device number)
other than the file system the root of the source directory is
on.
--exclude-regexpregexp
Exclude files matching the given regexp. Unlike the --exclude
option, this option does not match files in a directory it
matches. See the FILESELECTION section for more information.
--exclude-special-files
Exclude all device files, fifo files, socket files, and symbolic
links.
--exclude-sockets
Exclude all socket files.
--exclude-symbolic-links
Exclude all symbolic links. This option is automatically enabled
if the backup source is running on native Windows to avoid back-
ing-up NTFS reparse points.
--exclude-if-presentfilename
Exclude directories if filename is present. This option needs to
come before any other include or exclude options.
--force
Authorize a more drastic modification of a directory than usual
(for instance, when overwriting of a destination path, or when
removing multiple sessions with --remove-older-than). rdiff-
backup will generally tell you if it needs this. WARNING: You
can cause data loss if you mis-use this option. Furthermore, do
NOT use this option when doing a restore, as it will DELETE
FILES, unless you absolutely know what you are doing.
--group-mapping-filefilename
Map group names and ids according the the group mapping file
filename. See the USERSANDGROUPS section for more informa-
tion.
--includeshell_pattern
Similar to --exclude but include matched files instead. Unlike
--exclude, this option will also match parent directories of
matched files (although not necessarily their contents). See
the FILESELECTION section for more information.
--include-filelistfilename
Like --exclude-filelist, but include the listed files instead.
If filename is handwritten you probably want --include-globbing-filelist instead. See the FILESELECTION section for more
information.
--include-filelist-stdin
Like --include-filelist, but read the list of included files
from standard input.
--include-globbing-filelistfilename
Like --include-filelist but each line of the filelist will be
interpreted according to the same rules as --include and
--exclude.--include-globbing-filelist-stdin
Like --include-globbing-filelist, but the list of files will be
read from standard input.
--include-regexpregexp
Include files matching the regular expression regexp. Only
files explicitly matched by regexp will be included by this
option. See the FILESELECTION section for more information.
--include-special-files
Include all device files, fifo files, socket files, and symbolic
links.
--include-symbolic-links
Include all symbolic links.
--list-at-timetime
List the files in the archive that were present at the given
time. If a directory in the archive is specified, list only the
files under that directory.
--list-changed-sincetime
List the files that have changed in the destination directory
since the given time. See TIMEFORMATS for the format of time.
If a directory in the archive is specified, list only the files
under that directory. This option does not read the source
directory; it is used to compare the contents of two different
rdiff-backup sessions.
-l,--list-increments
List the number and date of partial incremental backups con-
tained in the specified destination directory. No backup or
restore will take place if this option is given.
--list-increment-sizes
List the total size of all the increment and mirror files by
time. This may be helpful in deciding how many increments to
keep, and when to --remove-older-than. Specifying a subdirec-
tory is allowable; then only the sizes of the mirror and incre-
ments pertaining to that subdirectory will be listed.
--max-file-sizesize
Exclude files that are larger than the given size in bytes
--min-file-sizesize
Exclude files that are smaller than the given size in bytes
--never-drop-acls
Exit with error instead of dropping acls or acl entries. Nor-
mally this may happen (with a warning) because the destination
does not support them or because the relevant user/group names
do not exist on the destination side.
--no-acls
No Access Control Lists - disable backup of ACLs
--no-carbonfile
Disable backup of MacOS X carbonfile information
--no-compare-inode
This option prevents rdiff-backup from flagging a hardlinked
file as changed when its device number and/or inode changes.
This option is useful in situations where the source filesystem
lacks persistent device and/or inode numbering. For example,
network filesystems may have mount-to-mount differences in their
device number (but possibly stable inode numbers); USB/1394
devices may come up at different device numbers each remount
(but would generally have same inode number); and there are
filesystems which don't even have the same inode numbers from
use to use. Without the option rdiff-backup may generate unnec-
essary numbers of tiny diff files.
--no-compression
Disable the default gzip compression of most of the .snapshot
and .diff increment files stored in the rdiff-backup-data direc-
tory. A backup volume can contain compressed and uncompressed
increments, so using this option inconsistently is fine.
--no-compression-regexpregexp
Do not compress increments based on files whose filenames match
regexp. The default includes many common audiovisual and ar-
chive files, and may be found in Globals.py.
--no-eas
No Extended Attributes support - disable backup of EAs.
--no-file-statistics
This will disable writing to the file_statistics file in the
rdiff-backup-data directory. rdiff-backup will run slightly
quicker and take up a bit less space.
--no-hard-links
Don't replicate hard links on destination side. If many hard-
linked files are present, this option can drastically decrease
memory usage. This option is enabled by default if the backup
source or restore destination is running on native Windows.
--null-separator
Use nulls (\0) instead of newlines (\n) as line separators,
which may help when dealing with filenames containing newlines.
This affects the expected format of the files specified by the
--{include|exclude}-filelist[-stdin] switches as well as the
format of the directory statistics file.
--parsable-output
If set, rdiff-backup's output will be tailored for easy parsing
by computers, instead of convenience for humans. Currently this
only applies when listing increments using the -l or --list-increments switches, where the time will be given in seconds
since the epoch.
--override-chars-to-quote
If the filesystem to which we are backing up is not case-sensi-
tive, automatic 'quoting' of characters occurs. For example, a
file 'Developer.doc' will be converted into ';068eveloper.doc'.
To override this behavior, you need to specify this option.
--preserve-numerical-ids
If set, rdiff-backup will preserve uids/gids instead of trying
to preserve unames and gnames. See the USERSANDGROUPS section
for more information.
--print-statistics
If set, summary statistics will be printed after a successful
backup. If not set, this information will still be available
from the session statistics file. See the STATISTICS section
for more information.
-r,--restore-as-ofrestore_time
Restore the specified directory as it was as of restore_time.
See the TIMEFORMATS section for more information on the format
of restore_time, and see the RESTORING section for more informa-
tion on restoring.
--remote-cmdcmd
Deprecated. Please use --remote-schema instead
--remote-schemaschema
Specify an alternate method of connecting to a remote computer.
This is necessary to get rdiff-backup not to use ssh for remote
backups, or if, for instance, rdiff-backup is not in the PATH on
the remote side. See the REMOTEOPERATION section for more
information.
--remote-tempdirpath
Adds the --tempdir option with argument path when invoking
remote instances of rdiff-backup.
--remove-older-thantime_spec
Remove the incremental backup information in the destination
directory that has been around longer than the given time.
time_spec can be either an absolute time, like "2002-01-04", or
a time interval. The time interval is an integer followed by
the character s, m, h, D, W, M, or Y, indicating seconds, min-
utes, hours, days, weeks, months, or years respectively, or a
number of these concatenated. For example, 32m means 32 min-
utes, and 3W2D10h7s means 3 weeks, 2 days, 10 hours, and 7 sec-
onds. In this context, a month means 30 days, a year is 365
days, and a day is always 86400 seconds.
rdiff-backup cannot remove-older-than and back up or restore in
a single session. In order to both backup a directory and
remove old files in it, you must run rdiff-backup twice.
By default, rdiff-backup will only delete information from one
session at a time. To remove two or more sessions at the same
time, supply the --force option (rdiff-backup will tell you if
--force is required).
Note that snapshots of deleted files are covered by this opera-
tion. Thus if you deleted a file two weeks ago, backed up imme-
diately afterwards, and then ran rdiff-backup with --remove-
older-than 10D today, no trace of that file would remain.
Finally, file selection options such as --include and --exclude
don't affect --remove-older-than.
--restrictpath
Require that all file access be inside the given path. This
switch, and the following two, are intended to be used with the
--server switch to provide a bit more protection when doing
automated remote backups. They are notintendedasyouronlylineofdefense so please don't do something silly like allow
public access to an rdiff-backup server run with --restrict-
read-only.
--restrict-read-onlypath
Like --restrict, but also reject all write requests.
--restrict-update-onlypath
Like --restrict, but only allow writes as part of an incremental
backup. Requests for other types of writes (for instance,
deleting path) will be rejected.
--server
Enter server mode (not to be invoked directly, but instead used
by another rdiff-backup process on a remote computer).
--ssh-no-compression
When running ssh, do not use the -C option to enable compres-
sion. --ssh-no-compression is ignored if you specify a new
schema using --remote-schema.--tempdirpath
Sets the directory that rdiff-backup uses for temporary files to
the given path. The environment variables TMPDIR, TEMP, and TMP
can also be used to set the temporary files directory. See the
documentation of the Python tempfile module for more informa-
tion.
--terminal-verbosity[0-9]
Select which messages will be displayed to the terminal. If
missing the level defaults to the verbosity level.
--test-server
Test for the presence of a compatible rdiff-backup server as
specified in the following host::filename argument(s). The
filename section will be ignored.
--use-compatible-timestamps
Create timestamps in which the hour/minute/second separator is a
- (hyphen) instead of a : (colon). It is safe to use this option
on one backup, and then not use it on another; rdiff-backup sup-
ports the intermingling of different timestamp formats. This
option is enabled by default on platforms which require that the
colon be escaped.
--user-mapping-filefilename
Map user names and ids according to the user mapping file file-name. See the USERSANDGROUPS section for more information.
-v[0-9],--verbosity[0-9]
Specify verbosity level (0 is totally silent, 3 is the default,
and 9 is noisiest). This determines how much is written to the
log file.
--verify
This is short for --verify-at-timenow--verify-at-timenow
Check all the data in the repository at the given time by com-
puting the SHA1 hash of all the regular files and comparing them
with the hashes stored in the metadata file.
-V,--version
Print the current version and exit

RESTORING

There are two ways to tell rdiff-backup to restore a file or directory.
Firstly, you can run rdiff-backup on a mirror file and use the -r or
--restore-as-of options. Secondly, you can run it on an increment
file.
For example, suppose in the past you have run:
rdiff-backup /usr /usr.backup
to back up the /usr directory into the /usr.backup directory, and now
want a copy of the /usr/local directory the way it was 3 days ago
placed at /usr/local.old.
One way to do this is to run:
rdiff-backup -r 3D /usr.backup/local /usr/local.old
where above the "3D" means 3 days (for other ways to specify the time,
see the TIMEFORMATS section). The /usr.backup/local directory was
selected, because that is the directory containing the current version
of /usr/local.
Note that the option to --restore-as-of always specifies an exact time.
(So "3D" refers to the instant 72 hours before the present.) If there
was no backup made at that time, rdiff-backup restores the state
recorded for the previous backup. For instance, in the above case, if
"3D" is used, and there are only backups from 2 days and 4 days ago,
/usr/local as it was 4 days ago will be restored.
The second way to restore files involves finding the corresponding
increment file. It would be in the /backup/rdiff-backup-data/incre-
ments/usr directory, and its name would be something like
"local.2002-11-09T12:43:53-04:00.dir" where the time indicates it is
from 3 days ago. Note that the increment files all end in ".diff",
".snapshot", ".dir", or ".missing", where ".missing" just means that
the file didn't exist at that time (finally, some of these may be gzip-
compressed, and have an extra ".gz" to indicate this). Then running:
rdiff-backup /backup/rdiff-backup-data/incre-
ments/usr/local.<time>.dir /usr/local.old
would also restore the file as desired.
If you are not sure exactly which version of a file you need, it is
probably easiest to either restore from the increments files as
described immediately above, or to see which increments are available
with -l/--list-increments, and then specify exact times into
-r/--restore-as-of.

TIME FORMATS

rdiff-backup uses time strings in two places. Firstly, all of the
increment files rdiff-backup creates will have the time in their file-
names in the w3 datetime format as described in a w3 note at
http://www.w3.org/TR/NOTE-datetime. Basically they look like
"2001-07-15T04:09:38-07:00", which means what it looks like. The
"-07:00" section means the time zone is 7 hours behind UTC.
Secondly, the -r,--restore-as-of,and--remove-older-than options take
a time string, which can be given in any of several formats:
1. the string "now" (refers to the current time)
2. a sequences of digits, like "123456890" (indicating the time in
seconds after the epoch)
3. A string like "2002-01-25T07:00:00+02:00" in datetime format
4. An interval, which is a number followed by one of the characters
s, m, h, D, W, M, or Y (indicating seconds, minutes, hours,
days, weeks, months, or years respectively), or a series of such
pairs. In this case the string refers to the time that preceded
the current time by the length of the interval. For instance,
"1h78m" indicates the time that was one hour and 78 minutes ago.
The calendar here is unsophisticated: a month is always 30 days,
a year is always 365 days, and a day is always 86400 seconds.
5. A date format of the form YYYY/MM/DD, YYYY-MM-DD, MM/DD/YYYY, or
MM-DD-YYYY, which indicates midnight on the day in question,
relative to the current timezone settings. For instance,
"2002/3/5", "03-05-2002", and "2002-3-05" all mean March 5th,
2002.
6. A backup session specification which is a non-negative integer
followed by 'B'. For instance, '0B' specifies the time of the
current mirror, and '3B' specifies the time of the 3rd newest
increment.

REMOTE OPERATION

In order to access remote files, rdiff-backup opens up a pipe to a copy
of rdiff-backup running on the remote machine. Thus rdiff-backup must
be installed on both ends. To open this pipe, rdiff-backup first
splits the filename into host_info::pathname. It then substitutes
host_info into the remote schema, and runs the resulting command, read-
ing its input and output.
The default remote schema is 'ssh -C %s rdiff-backup --server' where
host_info is substituted for '%s'. So if the host_info is
user@host.net, then rdiff-backup runs 'ssh user@host.net rdiff-backup
--server'. Using --remote-schema, rdiff-backup can invoke an arbitrary
command in order to open up a remote pipe. For instance,
rdiff-backup --remote-schema 'cd /usr; %s' foo 'rdiff-backup
--server'::bar
is basically equivalent to (but slower than)
rdiff-backup foo /usr/bar
Concerning quoting, if for some reason you need to put two consecutive
colons in the host_info section of a host_info::pathname argument, or
in the pathname of a local file, you can quote one of them by prepend-
ing a backslash. So in 'a\::b::c', host_info is 'a::b' and the path-
name is 'c'. Similarly, if you want to refer to a local file whose
filename contains two consecutive colons, like 'strange::file', you'll
have to quote one of the colons as in 'strange\::file'. Because the
backslash is a quote character in these circumstances, it too must be
quoted to get a literal backslash, so 'foo\::\\bar' evaluates to
'foo::\bar'. To make things more complicated, because the backslash is
also a common shell quoting character, you may need to type in '\\\\'
at the shell prompt to get a literal backslash (if it makes you feel
better, I had to type in 8 backslashes to get that in this man
page...). And finally, to include a literal % in the string specified
by --remote-schema, quote it with another %, as in %%.
Although ssh itself may be secure, using rdiff-backup in the default
way presents some security risks. For instance if the server is run as
root, then an attacker who compromised the client could then use rdiff-
backup to overwrite arbitrary server files by "backing up" over them.
Such a setup can be made more secure by using the sshd configuration
option command="rdiff-backup--server" possibly along with the
--restrict* options to rdiff-backup. For more information, see the web
page, the wiki, and the entries for the --restrict* options on this man
page.

FILE SELECTION

rdiff-backup has a number of file selection options. When rdiff-backup
is run, it searches through the given source directory and backs up all
the files matching the specified options. This selection system may
appear complicated, but it is supposed to be flexible and easy-to-use.
If you just want to learn the basics, first look at the selection exam-
ples in the examples.html file included in the package, or on the web
at http://rdiff-backup.nongnu.org/examples.htmlrdiff-backup's selection system was originally inspired by rsync(1),
but there are many differences. (For instance, trailing backslashes
have no special significance.)
The file selection system comprises a number of file selection condi-
tions, which are set using one of the following command line options:
--exclude, --exclude-filelist, --exclude-device-files, --exclude-fifos,
--exclude-sockets, --exclude-symbolic-links, --exclude-globbing-filelist, --exclude-globbing-filelist-stdin, --exclude-filelist-stdin,
--exclude-regexp, --exclude-special-files, --include, --include-filelist, --include-globbing-filelist, --include-globbing-filelist-stdin, --include-filelist-stdin, and --include-regexp. Each file
selection condition either matches or doesn't match a given file. A
given file is excluded by the file selection system exactly when the
first matching file selection condition specifies that the file be
excluded; otherwise the file is included. When backing up, if a file
is excluded, rdiff-backup acts as if that file does not exist in the
source directory. When restoring, an excluded file is considered not
to exist in either the source or target directories.
For instance,
rdiff-backup --include /usr --exclude /usr /usr /backup
is exactly the same as
rdiff-backup /usr /backup
because the include and exclude directives match exactly the same
files, and the --include comes first, giving it precedence. Similarly,
rdiff-backup --include /usr/local/bin --exclude /usr/local /usr
/backup
would backup the /usr/local/bin directory (and its contents), but not
/usr/local/doc.
The include, exclude, include-globbing-filelist, and exclude-globbing-filelist options accept extendedshellglobbingpatterns. These pat-
terns can contain the special patterns *, **, ?, and [...]. As in a
normal shell, * can be expanded to any string of characters not con-
taining "/", ? expands to any character except "/", and [...] expands
to a single character of those characters specified (ranges are accept-
able). The new special pattern, **, expands to any string of charac-
ters whether or not it contains "/". Furthermore, if the pattern
starts with "ignorecase:" (case insensitive), then this prefix will be
removed and any character in the string can be replaced with an upper-
or lowercase version of itself.
If you need to match filenames which contain the above globbing charac-
ters, they may be escaped using a backslash "\". The backslash will
only escape the character following it so for ** you will need to use
"\*\*" to avoid escaping it to the * globbing character.
Remember that you may need to quote these characters when typing them
into a shell, so the shell does not interpret the globbing patterns
before rdiff-backup sees them.
The --excludepattern option matches a file iff:
1.pattern can be expanded into the file's filename, or
2. the file is inside a directory matched by the option.
Conversely, --includepattern matches a file iff:
1.pattern can be expanded into the file's filename,
2. the file is inside a directory matched by the option, or
3. the file is a directory which contains a file matched by the
option.
For example,
--exclude /usr/local
matches /usr/local, /usr/local/lib, and /usr/local/lib/netscape. It is
the same as --exclude /usr/local --exclude '/usr/local/**'.
--include /usr/local
specifies that /usr, /usr/local, /usr/local/lib, and
/usr/local/lib/netscape (but not /usr/doc) all be backed up. Thus you
don't have to worry about including parent directories to make sure
that included subdirectories have somewhere to go. Finally,
--include ignorecase:'/usr/[a-z0-9]foo/*/**.py'
would match a file like /usR/5fOO/hello/there/world.py. If it did
match anything, it would also match /usr. If there is no existing file
that the given pattern can be expanded into, the option will not match
/usr.
The --include-filelist, --exclude-filelist, --include-filelist-stdin,
and --exclude-filelist-stdin options also introduce file selection con-
ditions. They direct rdiff-backup to read in a file, each line of
which is a file specification, and to include or exclude the matching
files. Lines are separated by newlines or nulls, depending on whether
the --null-separator switch was given. Each line in a filelist is
interpreted similarly to the way extendedshellpatterns are, with a
few exceptions:
1. Globbing patterns like *, **, ?, and [...] are not expanded.
2. Include patterns do not match files in a directory that is
included. So /usr/local in an include file will not match
/usr/local/doc.
3. Lines starting with "+ " are interpreted as include directives,
even if found in a filelist referenced by --exclude-filelist.
Similarly, lines starting with "- " exclude files even if they
are found within an include filelist.
For example, if the file "list.txt" contains the lines:
/usr/local
- /usr/local/doc
/usr/local/bin
+ /var
- /var
then "--include-filelist list.txt" would include /usr, /usr/local, and
/usr/local/bin. It would exclude /usr/local/doc,
/usr/local/doc/python, etc. It neither excludes nor includes
/usr/local/man, leaving the fate of this directory to the next specifi-
cation condition. Finally, it is undefined what happens with /var. A
single file list should not contain conflicting file specifications.
The --include-globbing-filelist and --exclude-globbing-filelist options
also specify filelists, but each line in the filelist will be inter-
preted as a globbing pattern the way --include and --exclude options
are interpreted (although "+ " and "- " prefixing is still allowed).
For instance, if the file "globbing-list.txt" contains the lines:
dir/foo
+ dir/bar
- **
Then "--include-globbing-filelist globbing-list.txt" would be exactly
the same as specifying "--include dir/foo --include dir/bar --exclude
**" on the command line.
Finally, the --include-regexp and --exclude-regexp allow files to be
included and excluded if their filenames match a python regular expres-
sion. Regular expression syntax is too complicated to explain here,
but is covered in Python's library reference. Unlike the --include and
--exclude options, the regular expression options don't match files
containing or contained in matched files. So for instance
--include '[0-9]{7}(?!foo)'
matches any files whose full pathnames contain 7 consecutive digits
which aren't followed by 'foo'. However, it wouldn't match /home even
if /home/ben/1234567 existed.

USERS AND GROUPS

There can be complications preserving ownership across systems. For
instance the username that owns a file on the source system may not
exist on the destination. Here is how rdiff-backup maps ownership on
the source to the destination (or vice-versa, in the case of restor-
ing):
1. If the --preserve-numerical-ids option is given, the remote
files will always have the same uid and gid, both for ownership
and ACL entries. This may cause unames and gnames to change.
2. Otherwise, attempt to preserve the user and group names for own-
ership and in ACLs. This may result in files having different
uids and gids across systems.
3. If a name cannot be preserved (e.g. because the username does
not exist), preserve the original id, but only in cases of user
and group ownership. For ACLs, omit any entry that has a bad
user or group name.
4. The --user-mapping-file and --group-mapping-file options over-
ride this behavior. If either of these options is given, the
policy described in 2 and 3 above will be followed, but with the
mapped user and group instead of the original. If you specify
both --preserve-numerical-ids and one of the mapping options,
the behavior is undefined.
The user and group mapping files both have the same form:
old_name_or_id1:new_name_or_id1
old_name_or_id2:new_name_or_id2
<etc>
Each line should contain a name or id, followed by a colon ":", fol-
lowed by another name or id. If a name or id is not listed, they are
treated in the default way described above.
When restoring, the above behavior is also followed, but note that the
original source user/group information will be the input, not the
already mapped user/group information present in the backup repository.
For instance, suppose you have mapped all the files owned by alice in
the source so that they are owned by ben in the repository, and now you
want to restore, making sure the files owned originally by alice are
still owned by alice. In this case there is no need to use any of the
mapping options. However, if you wanted to restore the files so that
the files originally owned by alice on the source are now owned by ben,
you would have to use the mapping options, even though you just want
the unames of the repository's files preserved in the restored files.

STATISTICS

Every session rdiff-backup saves various statistics into two files, the
session statistics file at rdiff-backup-data/session_statis-
tics.<time>.data and the directory statistics file at rdiff-backup-
data/directory_statistics.<time>.data. They are both text files and
contain similar information: how many files changed, how many were
deleted, the total size of increment files created, etc. However, the
session statistics file is intended to be very readable and only
describes the session as a whole. The directory statistics file is
more compact (and slightly less readable) but describes every directory
backed up. It also may be compressed to save space.
Statistics-related options include --print-statistics and --null-sepa-rator.
Also, rdiff-backup will save various messages to the log file, which is
rdiff-backup-data/backup.log for backup sessions and rdiff-backup-
data/restore.log for restore sessions. Generally what is written to
this file will coincide with the messages displayed to stdout or
stderr, although this can be changed with the --terminal-verbosity
option.
The log file is not compressed and can become quite large if rdiff-
backup is run with high verbosity.

EXIT STATUS

If rdiff-backup finishes successfully, the exit status will be 0. If
there is an unrecoverable (critical) error, it will be non-zero (usu-
ally 1, but don't depend on this specific value). When setting up
rdiff-backup to run automatically (as from cron(8) or similar) it is
probably a good idea to check the exit code.

BUGS

The gzip library in versions 2.2 and earlier of python (but fixed in
2.3a1) has trouble producing files over 2GB in length. This bug will
prevent rdiff-backup from producing large compressed increments (snap-
shots or diffs). A workaround is to disable compression for large
uncompressable files.

AUTHOR

Ben Escoto <ben@emerose.org>
Feel free to ask me questions or send me bug reports, but you may want
to see the web page, mentioned below, first.

SEE ALSO

python(1), rdiff(1), rsync(1), ssh(1). The main rdiff-backup web page
is at http://rdiff-backup.nongnu.org/. It has more information, links
to the mailing list and CVS, etc.
Version 1.3.3 MARCH 2009 RDIFF-BACKUP(1)